Recovery of locomotion after spinal cord hemisection: an X-ray study of the cat hindlimb

Hemisection of the spinal cord in adult cats is a suitable model to st udy the mechanisms underlying recovery of motor functions. The initial paresis of the hindlimb is followed by a considerable improvement of locomotor functions of the affected hindlimb. Kinematic analyses of treadmill locomotion were performed from 10 days to 8 months after complete hemisections (right side) of the spinal cord at the thoracolumbar level, using X-ray cinematography for precise measurements of the hindlimb joint angles. The footfall pattern and the electromyogram were recorded. Motor control of both proximal and distal hindlimb joints improved substantially during the 1st postoperative month. However, persistent locomotor deficits were still present several months after hemisection. They could be divided into three groups of symptoms: (1) The gait pattern was disturbed with regard to interlimb coordination. The stance-phase duration of the right hindlimb was shortened. (2) The flexor capacity of the affected hindlimb was reduced, resulting in a slow insufficient flexion of the hip, knee, and ankle during the swing phase. (3) The timing of the flexion-extension events was impaired. The onset of the E1-extension was delayed and the amplitude was reduced. Electromyographic patterns of muscle activity during locomotion of the lesioned side limb differed from the contralateral hindlimb, which served as a contro. The results indicate that in spite of a good short-term functional improvement there are long-term locomotor deficits present after spinal cord hemisection.